1. Field of the Invention
This invention is related generally to a flicker preventing circuit for use with a television receiver and more particularly to a flicker preventing circuit for use with a television receiver which will receive a character broadcasting signal such as a teletext signal.
2. Description of the Prior Art
Generally, a flicker is more perceptible to a viewer receiving a character broadcasting signal, such as a teletext signal, than in a conventional television signal. Referring to FIG. 1, there is seen a video signal S which rises very sharply, for example, a portion of a vertical line in a teletext signal. When such a signal is supplied to a cathode ray tube, the brightness distribution on the picture screen of the cathode ray tube caused by the signal S may be represented by a solid line curve l.sub.0 when an odd field is being displayed (the horizontal lines at this time are shown by the solid lines in FIG. 1). In an even field, however, the brightness distribution (the horizontal lines at this time are shown by the broken lines in FIG. 1) may be as shown by a broken line curve l.sub.e. Therefore, the brightness distribution moves up and down (the vertical scanning direction) as the fields alternate, so that, especially at the edge portion of the picture in the vertical direction, a flicker in the edge portion is very perceptible to a viewer.